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Analyse des spectres VLT pour l'expérience SNLS Qualification de transients cosmologiques

Abstract : The SuperNovae Legacy Survey (SNLS) experiment is an important part of the CFHT Legacy Survey, aiming at improved constraints on the Dark Energy equation of state through reducing the Univers expansion history uncertainty by type Ia supernovae (SN-Ia)
observations up to a redshift of 1.
The necessary standardisation in order to use SN-Ia's as a distance indicator relies on the precise measurment of their light curves in 4 filters (namely g', r', i' and z' for MegaCam at CFHT). The measurement of the recession velocity, via the redshift, and the validation of the transient as a SN-Ia proceed of the spectroscopic follow-up, achieved on four 8-m class telescops.
FORS1 instrument at ESO's Very Large Telescope provides most of this follow-up. The impressive data set, the usual weakness of the signal and the will of testing alternative image calibration and spectrum extraction algorithmes, lead me to develop an independent and automated reduction pipeline. The present work details a comprehensive technique, statistically based, for a homogeneous extraction of the transient spectra and of the host galaxy spectra, when those componants can actually be separated on the combined spectrogramm.
This by software development in C++ and Python, interacting with the photometric survey products : the deep field images and the transient's light curves. Then, the classification of the transients remains subjective but is enlightened by the simultaneous fit of the light curves and of the spectrum using SALT2 (an empirical model of SN-Ia, J.Guy 2007).
117 SN-Ia secure or probable (55% and 73% of the observations of the first and second year respectively) are identified this way.
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Contributor : Sylvain Baumont <>
Submitted on : Monday, January 11, 2010 - 5:52:41 PM
Last modification on : Monday, October 19, 2020 - 10:59:57 AM
Long-term archiving on: : Thursday, September 23, 2010 - 11:45:38 AM


  • HAL Id : tel-00196934, version 2


Sylvain Baumont. Analyse des spectres VLT pour l'expérience SNLS Qualification de transients cosmologiques. Astrophysique [astro-ph]. Université Paris-Diderot - Paris VII, 2007. Français. ⟨tel-00196934v2⟩



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